This class is used by the SVGGraphics2D SVG Generator to manage
addition of new Nodes to the SVG DOM Tree. This class handles
a set of DOMGroupManager objects that can all append to the
top level group managed by this class. This allows multiple
SVGGraphics2D instances, created from the same SVGGraphics2D
through the various create methods, to append to the same
SVG document and keep the rendering order correct.
The root node managed by this DOMTreeManager contains two children:
a top level group node and a top level defs node. The top level
defs node contains the definition of common SVG entities such as
the various AlphaComposite rules. Note that other defs can also be
created under the top level group, for example to represent
gradient or pattern paints.
[svg]
|
+-- [defs] Contain generic definitions
+-- [g] Top level group
|
+-- [defs] Contains definitions specific to rendering
+-- [g] Group 1
+-- ...
+-- [g] Group n

addOtherDef(Element definition)
Lets custom implementations for various extensions add
elements to the sections.

void

appendGroup(Element group,
DOMGroupManager groupManager)
When a group is appended to the tree by this call, all the
other group managers are requested to start new groups, in
order to preserve the Z-order.